Definitely "Time Trap" is the superior. "Counter-Clock" is notable for the Aprils. It had a nice sense of urgency with being pulled into the nova and the need to return home before they were too young. But how DID this universe survive?? I imagine people being "born" as corpses coming to live in caskets and "dying" as their reconnect the umbilical and jump into the womb. It makes reconnecting Spock's brain seem downright plausible in comparison!